Claw-pole rotor and production mehod therefor

ABSTRACT

The invention relates to an electric machine, in particular an alternator for motor vehicles, comprising a stator and a claw-pole rotor ( 15 ) that co-operates with the latter. The claw-poles of the rotor have claw-pole fingers ( 34 ) which are uniformly distributed around the periphery, axially intermesh in alternate directions at a distance from one another and comprise a pole core and an excitation winding. Permanent magnets are arranged between the claw-pole fingers ( 34 ) and are held in a retaining ring ( 42 ) with a zigzag configuration. To mount the retaining ring ( 42 ) in as simple a manner as possible between the claw-pole fingers ( 34 ), a longitudinal slit ( 38 ) is provided on each longitudinal side ( 37 ) of the claw-pole fingers ( 34 ). The retaining ring ( 42 ) engages in said slit by means of one respective longitudinal side of its axial sections ( 43 ).

BACKGROUND OF THE INVENTION

[0001] The invention relates to an electric machine, in particular athree-phase generator for motor vehicles according to the preamble ofclaim 1, and a method for producing a machine of this nature accordingto the preamble of claim 6.

[0002] An electric machine of this nature is made known in DE 199 39 808A1. According to said publication, the permanent magnets in the openspaces between the intermeshing claw-pole fingers are inserted into aretaining ring that absorbs the centrifugal forces acting on thepermanent magnets produced when the machine operates. The retaining ringis welded together with the adjacent claw-pole fingers on both sides ofits axial sections.

[0003] Using a “windingless rotor” as an example, a means of attainingthe object of the invention described hereinabove has the advantage thatwelding the retaining ring results in a permanent connection beingformed between the free claw pole conductive element and the claw poleplate situated on the rotor shaft, allowing the connection ring usedheretofore to be eliminated. Since, in the case of “slip-ring rotors”,both claw poles are usually mounted on the rotor shaft, a fixedconnection is not required there.

[0004] Rather, it has the disadvantage that a special working stepperformed at an additional processing station is required to make thewelded connections between the retaining ring and claw-pole fingers.

[0005] The goal of the present means of attaining the object of theinvention is to permit the simplest possible installation of theretaining ring between the claw-pole fingers.

ADVANTAGES OF THE INVENTION

[0006] Compared to the prior art, the electric machine according to theinvention having the characterizing features of claim 1 has theadvantage that the reconfiguration of the claw-pole fingers enables thecreation of nothing more than a positive connection between thepermanent magnets and the retaining ring, instead of a fixed connection.As such, the costly need to produce welded connections is eliminated,and the centrifugal forces acting on the retaining ring are stillreliably absorbed by the claw poles.

[0007] A further advantage is the fact that, due to the zigzagconfiguration of the retaining ring, the holders for the permanentmagnets no longer extend into the winding space for the excitationwinding, which means that an excitation winding having a largercross-section and, therefore, greater excitation power can now be housedin the claw-pole rotor.

[0008] Compared to the prior art, the method according to the inventionfor producing an electric machine according to the characterizingfeatures of claim 6 has the advantage that the retaining ring andpermanent magnets can be installed fully automatically between the clawpoles of the rotor on the existing assembly line for producing aclaw-pole rotor without permanent magnets at an additional assemblystation inserted there.

[0009] Advantageous further developments and embodiments of theinvention result from the remaining features listed in the dependentclaims.

[0010] As an additional means for restricting the elasticpressing-upward of the claw-pole fingers by the centrifugal forceswithin narrow limits, the longitudinal slits on the lateral flanks ofthe claw-pole fingers are interconnected via an end-face slit on the tipof the claw-pole fingers, into which said end-face slit a beadintegrally molded on the connection section of the retaining ringengages. Furthermore, to increase the bending stiffness of the axialsections of the retaining ring, it is advantageous to equip each of themwith a radially outwardly directed longitudinal hollow. Simpleproduction of the retaining ring can be attained by punching andstamping the retaining ring out of a piece of non-magnetic sheet metal.In the simplest manner possible, a punched-out sheet metal strip is usedthat is bent and stamped in the shape of an open retaining ring.

[0011] Although the inventive features can be used particularlyadvantageously with collector rings, they can also be realized on“windingless rotors”, provided that the fixed claw-pole connection iscreated there using additional means or measures. In that case, theconductive element forms one of the two claw poles.

[0012] In the production of the electric machine according to theinvention, axial longitudinal slits for accommodating the axial sectionsof the retaining ring are recessed in the lateral flanks of theclaw-pole fingers in a process step in preparation for assembly of theretaining ring. At an additional assembly station, the retaining ringwith a zigzag configuration is first inserted into the longitudinalslits in the claw-pole fingers of the first claw pole by means of onelongitudinal side of its axial sections. To accomplish this, the firstclaw pole is mounted on a tool holder that has a magnetic ring enclosingthe claw-pole fingers and the retaining ring from the outside, whichsaid magnetic ring is partially magnetized in the region of the axialsections of the retaining ring. To install the permanent magnets, theyare advantageously first inserted in an annular arrangement in axialholes of a round magazine. The round magazine is then positioned overthe exposed, end-face connection section of the retaining ring in such amanner that the axial holes with the permanent magnets come to rest inpairs between the connection sections of the retaining ring. Using anannular plunger having fingers matched with the holes in the roundmagazine that is located above the round magazine, the permanent magnetsare pushed axially out of the holes into the space between the claw-polefingers until the permanent magnets rest against each of the lateralflanks of a claw-pole finger. As they are pushed further, the permanentmagnets glide along the side of the lateral flanks of the claw-polefingers, thereby assuming an inclined position, where they are held bythe magnetic ring by means of its partial magnetization. After theplunger and the round magazine are removed, the permanent magnets areset into their final position on the axial sections of the retainingring by means of a shaped plunger having a claw pole-shaped contourplunging axially into the magnetic ring of the tool holder, where theyare held by the magnetic ring. The first subassembly which ispreassembled in this fashion is joined, together with the tool holderand the magnetic ring, with the rotor shaft, the pole core, theexcitation winding, and the second claw-pole, and the first claw-pole isplaced on the rotor shaft with an interference fit. The second claw-poleis placed on the rotor shaft with a sliding fit, then positioned by thefirst claw-pole and the retaining ring, and, finally, caulked with therotor shaft.

SUMMARY OF THE DRAWINGS

[0013] An exemplary embodiment of the invention is presented in thedrawings and described in greater detail.

[0014]FIG. 1 is a longitudinal sectional view of a three-phase generatorfor motor vehicles configured according to the invention,

[0015]FIG. 2 is a spacial representation of a first claw-pole of thealternator in FIG. 1,

[0016]FIG. 3 is a spacial representation of a retaining ring for thepermanent magnets,

[0017]FIG. 4 is a spacial representation of the first claw pole withinstalled retaining ring,

[0018]FIG. 5 is a spacial representation of an assembly station forinserting the permanent magnets,

[0019]FIG. 6 shows the assembly station in FIG. 5 with a shaped plungerfor positioning the permanent magnets,

[0020]FIG. 7 shows the assembly station in FIG. 6 with the first clawpole, the retaining ring, and the permanent magnets positioned thereinas the first subassembly,

[0021]FIG. 8 is a partial view of the assembly station in FIG. 7 withthe second subassembly comprising rotor shaft, pole ring and excitationwinding inserted in the first claw pole, and with the second claw polebefore assembly, and

[0022]FIG. 9 shows the assembled claw-pole rotor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023]FIG. 1 is a longitudinal sectional view of a three-phase generatorfor motor vehicles, the housing of which is composed substantially oftwo end shields 10 and 11 that are held together by screws 12, andbetween which the laminated stack 13 of a stator 14 is clamped. Aclaw-pole rotor 15 is located inside the stator bore, the excitationwinding 16 of which is wound on a pole core 17. A hub 18 is developed onthe left drive side of the generator in the end shield 10, in which saidhub a roller bearing 19 is located to support the drive-end part of arotor shaft 20. The right part of the rotor shaft 20 is supported in aroller bearing 21 having a weaker configuration, which said rollerbearing is located together with a collector-ring housing 22 in a hub 23of the end shield 11. A positive heat sink 24 and a negative heat sink25 of a rectifier, together with a protective cap 26, are mounted on thefront side of the rear end shield 11. A first and second claw pole 27,28 are pressed onto or caulked on the rotor shaft 20 on the front sideof the pole core 17. Two collector rings 29, 30 are secured in aninsulated manner to the rear shaft end to supply electricity to theexcitation winding 16. Said collector rings interact with the brushes ofa brush holder 31 secured on the rear end shield 11.

[0024] The claw poles 27 and 28 are produced out of pole plates by meansof cold forming. Each of them is composed of a pole disk 32 with a hole33 stamped in the center, and axially angled claw-pole fingers 34distributed evenly around the circumference. The claw-pole fingers 34 ofthe two claw poles 27 and 28 intermesh in alternate directions at adistance from one another, and they enclose the excitation winding 16.To increase the excitation power of the claw-pole rotor 15, a permanentmagnet 35 is located between each of the claw-pole fingers 34 and housedin a holder 36 in such a manner that is is supported against thecentrifugal forces acting on it when the machine operates.

[0025]FIG. 2 shows an enlarged spacial representation of the first clawpole 27 of the claw-pole rotor 15. Said figure shows that each of theclaw-pole fingers 34 has a longitudinal slit 38 created by means of chipremoval on its lateral flank 37, which said longitudinal slit extendsfrom the claw-pole base 39 to the claw-pole tip 40 in freely emergingfashion. The longitudinal slits 38 on the two lateral flanks 37 of eachclaw-pole finger 34 are interconnected on the claw-pole tip 40 of theclaw-pole fingers 34 by means of an end-face slit 41.

[0026]FIG. 3 shows the holder 36 for the permanent magnets 35 in theform of a zigzag-configured retaining ring 42 produced out ofnon-magnetic material that comprises alternating axial sections 43 andconnection sections 44, which said connection sections simultaneouslyfunction as axial stops for the permanent magnets 35. The retaining ring42 has been punched, bent and stamped out of a piece of sheet metal. Asan alternative, it can also be punched, bent and stamped as an openretaining ring out of a sheet metal strip, whereby the beginning and endof the sheet metal strip are preferably located in the center of anaxial section 43. Each of the axial sections 43 of the retaining ring 42is equipped with a radially outwardly arched longitudinal hollow 45 toincrease its bending stiffness. The connection sections 44 areconfigured—as shown in FIG. 3a—as bars 46 with a sheet metalcross-section that is rectangular, radially bent-upward, andframe-shaped, as shown along the line A-A in FIG. 3. This provides theconnection sections 44 with a high amount of bending stiffness againstthe centrifugal forces that occur there. It is greater than the bendingstiffness of the axial sections 43 in terms of the centrifugal forcesthat occur there.

[0027]FIG. 4 shows an enlarged spacial representation of the firstclaw-pole 27 in FIG. 2 with the retaining ring 42 in FIG. 3 pushed ontoits claw-pole fingers 34. Said FIG. 4 shows that each of the axialsections 43 rests against a lateral flank 37 of the claw-pole fingers 34by means of its one longitudinal side by engaging in the longitudinalslit 38 of the claw-pole fingers 34 recessed there, and the connectionsections 44 of the retaining ring 42 connect two adjacent axial sections43 with each other on each of the pole tips 40 of the claw-pole fingers34. Combined with FIG. 3, it is furthermore obvious in FIG. 4 that thebars 46 of the connection sections 44 are molded on over nearly theirentire width and angled radially inwardly on each of the end faces ofthe adjacent axial sections 43. This provides the retaining ring 42 witha high amount of stiffness against the centrifugal forces that act onit. Furthermore, the connection sections 44 form an axial stop when theretaining ring 42 is pushed onto the claw-pole fingers 34 of the clawpole 27. In this position, furthermore, a bead 47 integrally molded onthe connection sections 44 of the retaining ring 42 engages in the slit41 on the pole tip 40 of the claw-pole fingers 34.

[0028] Existing production lines can be used to produce the three-phasegenerator according to FIG. 1. Due to the novel method of holding thepermanent magnets in the claw-pole rotor 15 according to the invention,the production of the stator 14 and the two end shields 10 and 11remains unchanged. With regard for the claw-pole rotor 15 as well, itsindividual parts, e.g., rotor shaft 20, pole core 17, excitation winding16, claw poles 27 and 28, and the complete collector ring arrangementcan be produced first in unchanged fashion. The novel aspects, on theother hand, are the arrangement and holder 36 of the permanent magnets35 and their installation between the claw-pole fingers 34 when theclaw-pole rotor 15 is assembled. To accomplish this, as shown in FIG. 2,the axial longitudinal slits 38 for accommodating the axial sections 43of the retaining ring 42 are created first of all in the lateral flanks37 of the claw-pole fingers 34 of the two claw poles 27 and 28.Furthermore, to hold the permanent magnets 35, the retaining ring 42composed of non-magnetic material is die-cut out as shown in FIG. 3 withthe axial sections 43 and the connection sections 44 out of a piece ofsheet metal and then bent and stamped in the shape shown in FIG. 3. Theretaining ring 42 is then pushed, first of all, in the axial directiononto the claw-pole fingers 34 of the first claw pole 27 by pushing onelongitudinal side each of its axial sections 43 as shown in FIG. 4 intothe longitudinal slits 38 in the claw-pole fingers 34 until the rearconnection sections 44 rest against the pole tips 40 of the claw-polefingers 34.

[0029] As shown in FIG. 5, the first claw pole 27 with the retainingring 42 is now mounted on a tool holder 50, whereby a magnetic ring 51is mounted on the tool holder 50, said magnetic ring enclosing the clawpole 27 with its claw-pole fingers 34 and the retaining ring 42 from theoutside, thereby surrounding said parts. The magnetic ring 51 ispartially magnetized in the region of the axial sections 43 of theretaining ring 42. The only difference between the tool holder 50 andthe prior art is the addition of the magnetic ring 51.

[0030] Novel features, on the other hand, are the devices shown in FIGS.5 and 6 for inserting and positioning the permanent magnets 35 in theretaining ring 42. To accomplish this, round magazines 52 are firstloaded with the permanent magnets 35 at another location by placing saidpermanent magnets in appropriately-sized axial holes 53 of the roundmagazine 52. The round magazines loaded in this fashion can be deliveredon pallets. To produce the claw-pole rotor 15, then, one round magazine52 each is taken from a not-shown pallet of this nature and positionedover the tool holder 50 as shown in FIG. 5. The axial holes 53 with thepermanent magnets 35 are held in their axial position in an annularconfiguration using vacuum by means of a valve housing 54 located aboveit and to be moved axially, using the known pick-and-place technique.The round magazine 52 is positioned on the valve housing 54 by means ofpins 55 in the valve housing 54 that engage in axial holes 56 in theround magazine 52. An annular plunger 57 is located above the valvehousing 54, which said annular plunger is axially displaceable as welland comprises axially projecting fingers 58 on its underside which arealso arranged in the shape of a ring and that are matched with the axialholes 53 in the round magazine 52. The round magazine 52, valve housing54 and plunger 57 are now moved toward the tool holder 50 and positionedon the exposed, end-face connection sections 44 in such a manner thatthe axial holes 53 with the permanent magnets 35 come to rest in pairsbetween the connection sections 44. The set of permanent magnets 35located in the round magazine 52 is then pushed axially by the fingers58 of the annular punch 57 out of the holes 53 into the space betweenthe claw-pole fingers 34 until the permanent magnets 35 rest againsteach of the lateral flanks 37 of a claw-pole finger 34. When thepermanent magnets 35 are pushed further by the fingers 58 of the plunger57, the permanent magnets finally glide along each of the lateral flanks37 of a claw-pole finger 34 and assume an inclined position. Due to thepartial magnetization of the magnetic ring 51, the permanent magnets 35are held in this position at first, so that the round magazine 52 withthe valve housing 54 and the plunger 57 can be removed.

[0031]FIG. 6 shows the tool holder 50 with the magnetic ring 51 and theset of permanent magnets 35 in the aforementioned inclined position. Itis obvious in this figure as well that the permanent magnets 35 aredesigned in the shape of bars and have a trapezoidal cross-section thatincreases in size as it extends outward. In order to bring the permanentmagnets 35 into their final position underneath the axial sections 43 ofthe retaining ring 42, a shaped plunger 59—as shown in FIG. 6—is nowbrought into position over the tool holder 50 with the magnetic ring 51.Said shaped plunger plunges axially with a claw-shaped contour 60 intothe magnetic ring 51, and each of its claw tips 61 is guided between thepaired, inclined permanent magnets 35. Finally, the permanent magnets 35are set in their final position, where they are held when the shapedplunger 59 is then removed from the magnetic ring 51.

[0032]FIG. 7 shows the tool holder 50 with the magnetic ring 51 and withthe permanent magnets 35 located in their final position, each one onthe inside of an axial section 43 of the retaining ring 42. The firstclaw pole 27, together with the retaining ring 42 and the permanentmagnets 35, forms a first subassembly.

[0033] In another production step, the rotor shaft 20 is preassembled inknown fashion with the pole core 17 and the excitation winding 16 toform a second subassembly. As shown in FIG. 8, the first preassembledsubassembly on the tool holder 50, together with the magnetic ring 51,is now joined with the aforementioned second subassembly. The first clawpole 27 is placed on a knurled section of the rotor shaft 20 and fixedin position. FIG. 8 also shows that the excitation winding is enclosedby a paper insulation 62 that is fixed in position by a binding 63, andon the top front side of which the wire ends 64 of the excitationwinding are guided out for connection to the collector ring arrangement47. To produce the claw-pole rotor 15, the second claw pole 28 is nowplaced axially on the exposed end of the rotor shaft in a furtherworking step. The claw-pole fingers 34 of said claw-pole rotor engagebetween the claw-pole fingers 34 of the first claw pole 27 in the gapsbetween the axial sections 43 of the retaining ring 42. The longitudinalsides of the axial sections 43 of the retaining ring 42 that are stillfree are then pushed into the longitudinal slits 38 in the claw-polefingers 34 of the second claw pole 28. The second claw pole 28 ispositioned by means of its sliding fit in the circumferential directionon the rotor shaft 20 by means of the first claw pole 27 and theretaining ring 42. After it is positioned on the rotor shaft 20, it isfinally fixed in position by means of caulking. In a further workingstep, the collector ring arrangement 47 can now be placed on the top endof the rotor shaft 20, as usual.

[0034]FIG. 9 shows the fully-assembled claw-pole rotor 15 with theretaining ring 42 configured according to the invention, each of theaxial sections 43 of which is located between two adjacent claw-polefingers 34, and that rest in a longitudinal slit of a lateral flank 37of the claw-pole fingers 34 by means of their longitudinal sides. Thepermanent magnets are enclosed and held from the outside by the lateralflanks 37 of the claw-pole fingers 34 and by the connection sections 44on the side, and by the axial sections 43 of the retaining ring 42. Theyare further fixed in position between the claw-pole fingers 34 by meansof a common dipping impregnation procedure. Additionally, before therotor is assembled with the stator, they are magnetized with alternatingpolarity in the circumferential direction of the rotor by magneticfields applied to the claw-pole fingers 34 from the outside.

What is claimed is:
 1. An electric machine, in particular an alternatorfor motor vehicles, comprising a stator (14) carrying a stator windingand a claw-pole rotor (15) that co-operates with said stator, comprisinga pole core (17) surrounded by an excitation winding (16) and twoclaw-poles (27, 28) mounted on a rotor shaft (20), which said claw-polesare uniformly distributed around the periphery and have claw-polefingers (34) that intermesh axially in alternate directions at adistance from one another, whereby at least one permanent magnet (35) isarranged between the adjacent claw-pole fingers (34) and is held by anon-magnetic holder (36) and supported against centrifugal forces, andwhereby the holder (36) of the permanent magnets (35) is composed of aretaining ring (42) with a zigzag configuration, each of the axialsections (43) of which said retaining ring is located between twoadjacent claw-pole fingers (34) and rest by means of their longitudinalsides on each lateral flank (37) of the claw-pole fingers (34), and eachof the connection sections (44) of which said retaining ring connect twoadjacent axial sections (43) with each other on the pole tip (40) of theclaw-pole finger (34), wherein the retaining ring (42) engages in alongitudinal slit (38) on the lateral flanks (37) of the claw-polefingers (34) by means the longitudinal sides of its axial sections (43).2. The electric machine according to claim 1, wherein the longitudinalslits (38) on the lateral flanks (37) are interconnected with each othervia an end-face slit (41) on the pole tip (40) of the claw-pole finger(34), into which said slits a bead (47) integrally molded on theconnection section (44) of the retaining ring (42) engages.
 3. Theelectric machine according to claim 1 or 2, wherein each of the axialsections (43) is equipped with a radially outwardly directedlongitudinal hollow (45) for increasing its bending stiffness.
 4. Theelectric machine according to one of the preceding claims, wherein theretaining ring (42) is punched, bent and stamped out of a piece of sheetmetal.
 5. The electrical machine according to claim 4, wherein theretaining ring (42) is bent and stamped out of a punched-out sheet metalstrip to form an open ring.
 6. A method for producing an electricalmachine, in particular a three-phase generator for motor vehiclesaccording to the preamble of claim 1, wherein a longitudinal slit (38)is recessed into each of the lateral flanks (37) of the claw-polefingers (34), and wherein the retaining ring (42) with a zigzagconfiguration is pushed onto the claw-pole fingers (34) of the firstclaw-pole (27) in the axial direction in such a manner that the axialsections (43) are pushed into the longitudinal slit (38) by means oftheir one longitudinal side, so that the permanent magnets (35) are theninserted in the axial sections (43) of the retaining ring (42), so thata first subassembly is produced, onto which one end of the rotor shaft(20) is placed, and, finally, the second claw-pole (28) with itsclaw-pole fingers (34) is inserted between the claw-pole fingers (34) ofthe first claw-pole (27) in such a manner that the retaining ring (42)is thereby pushed onto the claw-pole fingers (34) of the secondclaw-pole (28) in the axial direction as well by the fact that the axialsections (43) of the retaining ring (42) are inserted by means of theirother longitudinal side into the longitudinal slit (38) of the claw-polefinger (34) of the second claw-pole (28).
 7. The production methodaccording to claim 6, wherein the rotor shaft (20) with the pole core(17) and the excitation winding (16) are preassembled to form a secondsubassembly.
 8. The production method according to claim 7, wherein thesecond claw-pole (28) is placed on the other end of the rotor shaft(20).
 9. The production method according to one of the claims 6 through8, wherein the first claw-pole (27) is mounted on a tool holder (50)that has a magnetic ring (42) enclosing the claw-pole fingers (34) andthe retaining ring (42) from the outside, which said magnetic ring ispartially magnetized in the region of the axial sections (43) of theretaining ring (42).
 10. The production method according to claim 9,wherein the permanent magnets (35) are inserted first of all in anannular arrangement in axial holes (53) of a round magazine, and whereinthe round magazine (52) is then positioned over the exposed, end-faceconnection section (43) of the retaining ring (42) in such a manner thatthe axial holes (53) with the permanent magnets (35) come to rest inpairs between the connection sections (44) of the retaining ring (42).11. The production method according to claim 10, wherein a round plunger(57) having fingers (58) matched with the holes (53) in the roundmagazine (52) is located above the round magazine (52), and said fingerspush the permanent magnets (35) axially out of the holes (53) into thespace between the claw-pole fingers (34) until the permanent magnets(35) rest against each of the lateral flanks (37) of a claw-pole finger(34) and then glide along the side of said claw-pole finger, therebyassuming an inclined position, where they are held by the magnetic ring(51).
 12. The production method according to claim 11, wherein, afterthe plunger (57) and the round magazine (52) are removed, the permanentmagnets (35) are set in their final position on the axial sections (43)of the retaining ring (42) by means of a shaped plunger (59) having aclaw pole-shaped contour (60) plunging axially into the magnetic ring(51) of the tool holder (50), and said permanent magnets are held insaid final position by the magnetic ring (51).
 13. The production methodaccording to claim 12, wherein the first subassembly which ispreassembled in this fashion is joined, together with the magnetic ring(51), with the second subassembly and the second claw-pole (28), and thefirst claw-pole (27) is placed on the rotor shaft (20) of the secondsubassembly with an interference fit.
 14. The production methodaccording to claim 13, wherein the second claw-pole (28) is placed onthe rotor shaft (20) with a sliding fit, then positioned by the firstclaw-pole (27) and the retaining ring (42), and, finally, secured on therotor shaft (20), preferably by caulking it with said rotor shaft.